Method of decolorizing ester distillation fractions



Patented Aug. 2, 1932 UNITED STATES PATENT OFFICE EDWIN H. CARNARIUS AND VERN E D. CHARLESTON, OF PEORIA, ILLINOIS, ASSIGNORS TO COMMERCIAL SOLVENTS CORPORATION, OF TERRE HAUTE, INDIANA, A. CORPO- RATION OF MARYLAND METHOD OF DEOOLORIZING- ESTER DISTILLATION FRACTION$ No Drawing.

This invention relatesto the decolorization of colored fractions obtained in the distillation of volatile aliphatic compounds, especially aliphatic esters.

In the manufacture of butyl acetate, butyl lactate, and other esters, in the separation of the solvents obtained in the butyl-acetonic fermentation, and in the distillation of aliphatic organic compounds generally, colored fractions are often obtained, especially fractions having a greenish-yellow color. This phenomenon is found especially in the head products of the distillations, i. e., the first fractions to distill over.

For example, in the manufacture of butyl acetate, especially from impure acetic acid, head products of a greenish-yellow color are obtained. Since this coloring matter is volatile and comes over with the esters, it

29 has been found in the past to be very difficult to remove, and since the colored fractions amount to over 1% of the total ester, a considerable quantity of the material is soon built up which, unless decolorized,

would have little commercial value.

It has now been found that the color may be efficiently and economically removed by treating the liquid with oxidizing agents. Agents which are known to be capable of 39: oxidizing organic compounds, for example,

bleaching powder, sodium, potassium, or calcium hypochlorite, an alkali metal dichromate or permanganate, etc. have been found to be suitable for this purpose.

The method for carrying out this invention may best be illustrated by the following example. The colored head products from butyl acetate, amounting to about 300 gals. from each 22,000 gals. charge, are stored until a sufiicient volume to be economically worked up is obtained. The material is then rectified, whereby it is concentrated about and it is then pumped to a mixing tank where it is thoroughly mixed with saturated aqueous solution of calcium hypochlorite amounting to about 1 lb. of the bleaching powder per 5 gals. of the liquid to be treated.

. The agitation is continued for about 12 hours, and the mixture is then allowed to settle. The decolorized material is decanted, washed Application filed October 24, 1930. Serial No. 491,078.

with about one volume of water to six volumes of the liquid, decanted again and pumped directly to a still where the material is finally rectified as a water-white product.

There is some evidence (for example, the formation of an addition product with sodium bisulphite) that the colored matter in the case of the butyl acetate head products is a carbonyl compound, but this invention 1s not to be limited to any theoretical considerations of the substances or equations example or an equivalent amount of another oxidizing agent will be found to be satisfactory.

Other modifications may be made in the process, such as treating with the oxidizing agent at temperatures other than atmospheric or Varying the time of agitation, as may be found to be desirable in any particular case. A caustic wash may be made after the treatment with the oxidizing agent and prior to the water wash, to remove any acid which might be liberated during the treatment. The oxidizing agent may be added in a different manner from that specified in the example; for instance, finely divided solid material may be added, or gaseous chlorinemay be bubbled through the liquid. In the latter case a weak alkaline material, such as sodaash, should be added in order to prevent any hydrolyzing action by the chlorine. In case only a small amount of coloring matter is present, it may be found desirable to efiect the treatment with the oxidizing agent directly in the column. Using this method, a

solution of the oxidizing agent may be dropped in at the top of the column, but as it is preferable to avoid prolonged contact of oxidizing agents with the organic liquids at high temperatures, the treatment could be effected in one or more plates of the column, by-passing the reflux around these plates.

After the oxidation treatment by the agitation method, the oxidizing agent may be removed by other means than decantation, if desired, for example by distillation methods. This latter procedure would be necessary if the liquid were miscible with water, but in the case of butyl acetate head products, the decantation method is preferred, especially in View of the fact that the liquid is subsequently to be washed before distillation.

It is to be understood, then, that this process is in no way to be limited to the exact materials or conditions of operation specified above, but that such changes or modifications as would occur to one skilled in the art may be incorporated without departing from the spirit or scope of the invention.

The invention now having been described, what is claimed is:

1. A process for the decolorization of colored fractions obtained in the distillation of aliphatic monocarboxylic acid esters which comprises agitating said colored fractions with an oxidizing agent, removing any unreacted oxidizing agent and such reaction products as are not dissolved in the treated, fractions, and subsequently distilling said treated fractions.

2. A process for the decolorization of colored fractions obtained in the distillationof aliphatic monocarboxylic acid esters which comprises agitating said colored fractions with bleaching powder, removing any unreacted bleaching powder and such reaction products as are not dissolved in the treated fractions and subsequently distilling said treated fractions.

3. A process for the decolorization of colored fractions obtained in the distillation of aliphatic monocarboxylic acid esters which comprises agitating said colored fractions with at least one material chosen from the roup consisting of calcium hypochlorite, alkali metal hypochlorites, alkali metal dichromates, and alkali metal permanganates, removing any of said material which has not undergone reaction and such reaction prod ucts as are not dissolved in the treated fractions, and subsequently distilling said treated fractions.

4. A process for the decolorization of butyl acetate head products which comprises agitating said head products with an oxidizing agent, removing any unreacted oxidizing agent and such reaction products as are not dissolved in the treated head products, and subsequently distilling said treated head products.

5. A process for the decolorization of butyl acetate head products which comprises agitating said head products with bleaching powder, removing any unreacted bleaching powder and such reaction products as are not dissolved in the treated head products, and subsequently distilling said treated head products.

6. A process for the decolorization of butyl acetate head products which comprises agitating said head products with at least one material chosen from the group consisting of calcium hypochlorite, alkali metal hypochlorites, alkali metal dichromates, and alkali metal permanganates, removing any of said material which has not undergone reaction and such reaction products as are not dissolved in the treated head products, and subsequently distilling said treated head products.

7. In a process for the decolorization of colored fractions obtained in the distillation of aliphatic monocarboxylic acid esters, the step which comprises treating said colored fractions with an oxidizing agent.

8. In a process for the decolorization of colored fractions obtained in the distillation of aliphatic monocarboxylic acid esters, the step which comprises treating said colored fractions with bleaching powder.

9. In a process for the decolorization of colored fractions obtained in the distillation of aliphatic monocarboxylic acid esters, the step which comprises treating said colored fractions with at least one material chosen from the group consisting of calcium hypochlorite, alkali metal hypochlorites, alkali metal dichromates, and alkali metal permanganates.

10. In a process for the decolorization of butyl acetate head products, the step which comprises treating said head products with an oxidizing agent.

11. In a process for the decolorization of butyl acetate head products, the step which comprises treating said head products with bleaching powder.

12. In a process for the decolorization of butyl acetate head products, the step which comprises treating said head products with at least one material chosen from the group consisting of calcium hypochlorite, alkali metal hypochlorites, alkali metal dichromates, and alkali metal permanganates.

In testimony whereof we afl'ix our signatures.

EDWIN I-I. CARNARIUS. VERNE D. CHARLESTON.

n. all) 

